The present invention relates to a microcomputer, and, more particularly, to an effective art obtained by applying to a microcomputer that is suitable for the control of cooling equipment and the brightness control of a display device in the microcomputer formed on one chip, what is called a one-chip microcomputer.
According to what this inventor investigated, the following art is taken into consideration concerning a microcomputer.
For instance, a one-chip microcomputer used in a notebook-size personal computer as an example of the microcomputer is composed of a CPU (Central Processing Unit) that performs operation processing, a CPG (Clock Pulse Generator) that generates a clock signal, a flash memory that stores control programs, a RAM (Random Access Memory) that stores data, an A/D (Analog/Digital) circuit or a D/A (Digital/Analog) circuit that controls peripheral equipment, such as a cooling fan and a LCD (Liquid Crystal Display), an I/O (Input/Output) circuit that is connected to an external device, and a bus interface, which are formed on one chip.
Moreover, in this type of microcomputer, in order to control a back-light power supply of the LCD, for instance, there is an art of a microcomputer for liquid crystal display in which a PWM (Pulse Width Modulation) circuit that generates a desired voltage by varying High and Low periods was mounted in one chip (refer to patent Publication 1, for instance).
[Patent Publication 1]
Japanese Patent Laid-Open No. Hei 9(1997)-6934